The bacterial mRNA's and proteins produced by a set of specialized transducing phages that carry overlapping segments of the genes coding for the Escherichia coli K-12 isoleucine-valine genetic region will be identified and characterized. These specialized transducing phages will be examined for the presence of regulatory elements required for the normal expression of the isoleucine-valine genes. Ultraviolet irradiated bacteria will be infected with bacteriophage in the presence of radioactive amino acids, and autoradiograms will be prepared following gel electrophoresis. DNA will be isolated from selected bacteriophage and used in an in virto system to direct the synthesis of radioactively labelled proteins that will be detected electrophoresis and autoradiography. Preliminary experiments indicate that bacterial specific proteins can be detected in such systems, and that they are distinguishable from phage specific proteins. The production of mRNA corresponding to the isoleucine-valine genes will be examined by gel electrophoresis of labelled RNA produced in a purified system containing DNA, RNA polymerase, and nucleotide percursors. The bacterial and bacteriophage genes present in these specialized transducing phage will be characterized by transduction, heteroduplex formation and restriction enzyme analysis. These studies will permit an identification of the isoleucine-valine gene products and of the control elements that regulate their expression.